Device for determining the wetting of a wall by a liquid

ABSTRACT

Ultrasonic waves passing through guides ( 5, 6 ) are emitted towards a target ( 2 ) immersed in a liquid in order to infer the wetting of this target from certain features of the received signal. The invention is notably applied to the study of liquid heavy metals.

The object of this invention is a device for determining the wetting ofa wall by a liquid.

Certain fields of the art require that one be concerned with this issueand for example determine whether walls of tanks, piping, measurementprobes or of nuclear reactor tools, are wetted with certain metals whichmay be sodium, potassium, lead, bismuth or their alloys. Depending onthe case, wetting is essential or forbidden on the contrary.

The wetting of a solid by a liquid is a phenomenon which depends on manyfactors including, in addition to the chemical nature of the liquidmetal and of the wall, the purity of the liquid, the state of thesurface of the wall, the temperature, the nature and presence ofoccluded gases in the liquid and the time for putting the liquid metalin the presence of the wall. Wetting may be defined as the adhesion ofthe metal on the wall at an atomic scale and it is not easy to determineit directly. Different criteria and measurement methods have beencontemplated for determining the wetting, its absence or an intermediatestate on the walls of an object immersed in a liquid metal bath, byoperating, if necessary, on a control specimen of the object.

So the idea of correlating wetting with the spreading of a drop or withthe capillary rising of the liquid metal dawned upon us, withoutobtaining a very accurate result, because of the numerous influencingfactors.

The invention belongs to a different category of methods and comprisestwo fundamental embodiments, but which are closely related as they arebased on the transmission of ultrasonic waves through the interface ofthe wall and of the liquid. One of them is a device for determining thewetting of a wall by a liquid, characterized in that it comprises: acapacity for the liquid; a control object of the wall placed in thecapacity; an emitter and a receiver of ultrasonic waves; and twowaveguides passing through the capacity, located in extension, theemitter and the receiver being respectively mounted on ends of thewaveguides extending out of the capacity, and the object being placedbetween the waveguides; the object having a thickness selected forfavoring the passage of waves from the emitter. And the other one is adevice for determining the wetting of a wall by a liquid, characterizedin that it comprises: a capacity for the liquid; a control object of thewall placed in the capacity; an emitter and a receiver of ultrasonicwaves; and two waveguides passing through the capacity locatedside-by-side, the emitter and the receiver being respectively mounted onends of the waveguides extending out of the capacity, and the objectbeing placed in front of the waveguides, the object having a frontsurface selected for favoring reflections of the waves between thewaveguides.

In many tangible cases, when the investigated liquid is a molten metal,the capacity should be equipped with heating means; the waveguides willthen be equipped with cooling means located outside the capacity, andwhich may consist of a casing surrounding each of the waveguides betweenthe capacity and either the emitter or the receiver.

The invention will now be described in all its developments by means ofthe following figures:

FIG. 1 is a general view of the device according to the invention,

FIGS. 2A, 2B, 2C and 2D illustrate the involved signals,

and FIGS. 3A and 3B, 4, 5 and 6A, 6B and 6C illustrate other embodimentsof the invention.

FIG. 1 describes a first embodied device of the invention. It is formedin an enclosure 1 which allows the atmosphere with a desired compositionto be blown therein and contains a target 2 which is an imitation of thewall to be investigated and which is found, supported by a support 3, ina capacity 4 included in the enclosure 1. Two waveguides 5 and 6 facingeach other penetrate the capacity 4 and stop at a certain distance fromthe target 2. The seal of the capacity 4 is guaranteed by passagewaysleeves 7 for the waveguides 5 and 6, the ends of which are soldered tothe capacity 4 and to a protruding flange 20 at a section of thewaveguides 5 and 6 outside the capacity 4. Bellows 8 extend thepassageway sleeves 7 and extend up to brackets 9 connected to casings 10themselves attached from the rear to the enclosure 1. The bottom of thecasings 10 (near brackets 9) is occupied by water cases 11, the contentsof which are renewed through inlet and outlet conduits 12 and 13. Thewaveguides 5 and 6 pass through the water cases 11 which are recessed intheir center, and their ends are equipped with supports 14 of ultrasonicwave transducers 15 and 16, the first of which is for emittingultrasonic waves and the second one is for receiving them. Referencenumber 17 overall designates a supporting structure of the capacity 4 inthe enclosure 1 and reference number 18 designates means for heating thecapacity 4 in order to conduct the experiment at the desiredtemperature. Double soldering of the passageway sleeves 17 makes thecapacity 4 leak-proof, and the water cases 11 form cooling means whichacts as a barrier to heat flowing through the waveguides 5 and 6 andwhich might have reached transducers 15 and 16. The bellows 8 coveringthe hot portion of the waveguides 5 and 6 protect the outside. A heatshield 19 is also positioned around capacity 4.

The following figures show a few examples of signals obtained with theinvention through a wetting liquid, the upper trace illustrating theemitted signal and the lower trace the received signal. On FIG. 2A, thetarget 2 was removed; in the case of FIG. 2B, the target was set up inthe wet state; in the case of FIG. 2C, it was set up but not wetted;finally FIG. 2D illustrates an intermediate (partial) wetting of thetarget 3. Total or partial absence of wetting was reproduced bysimulation, by covering the target 2 with an adhesive sheet under whichgas was occluded.

The thickness of the target 2 is selected in order to provide maximumtransparence and more specifically, it is equal to the half-wavelengthof the applied ultrasound. FIG. 2A shows liquid which produces moderatedamping of the waves with the appearance of a large receiver signal (462millivolts at the origin).

Each of the signals also comprises, after the first wave train whichrepresents the provided pulse, successive echoes produced by multiplereflections at the ends of the waveguide 5 or 6.

FIG. 2B shows the influence of the damping by the target 2, with only asubsisting 70 millivolt signal. It is also noted that the signalmeasured on the side of the emitting waveguide 5 comprises echoes fromreflections of the waves on target 2.

FIG. 2C shows the nearly complete disappearance of the received signal,the emitted energy then being absorbed on the surfaces of the target 2.Finally, the results obtained in FIG. 2D are intermediate with a valueat the origin of 40 millivolts.

Hence, the wetting level of the target 2 appears as being proportionalto the intensity of the signal which was able to pass through the target2, of course depending on the intensity of the emitted signal. Theintensity at the origin of the received signal is what should beconsidered.

Certain changes in the design completely discussed above will now bepresented more succinctly. It is thus seen in FIG. 3A, that thewaveguides 5 and 6 may be positioned side by side if the targetreferenced here by 30, is of an appropriate shape, for example a concaveshape, and sends back the waves issued from the first waveguide 5towards the second one (6) after having undergone two reflections in anotch 31. As shown in FIG. 3B, a sealed assembly of the waveguides 5 and6 through the wall of the capacity 4 is achieved by soldering saidguides, at the location of a flange 32, to a bracket 33 blocking anaperture of the capacity wall 4. Waveguides 5 and 6 pass throughrespective apertures of the bracket 33. A seal gasket 34 is tightlyfitted between the capacity 4 and the bracket 33.

In the embodiment of FIG. 4, waveguides 5 and 6 are no longer parallelbut convergent, the target 35 being now concave and only one wavereflection is produced on it. In FIG. 5, both waveguides 5 and 6 arepositioned at a right angle, a reflection being produced on a target 36which is now of a planar shape.

FIGS. 6A and 6B illustrate further embodiments of another design,wherein similar waveguides 5 and 6 are replaced with concentricwaveguides, including an interior waveguide 38 like the previous ones(cylindrical) and an external tubular waveguide 39. In the embodiment ofFIG. 6A, the interior waveguide is the emitter and waves undergo doublereflection on a target 40 provided with a circular notch 41 having atriangular section as in FIG. 3A. However, in the embodiment of FIG. 6B,the external waveguide 39 is the emitter and the waves are reflectedtowards the entrance of the interior waveguide 38 after having undergonea reflection on a target 42 provided with a rounded imprint like theprevious target 35.

The embodiment of the rear of the device may be that of FIG. 6C, theexternal waveguide 39 comprising a flange 43 soldered to a bracket 44screwed to the wall of the capacity 4 and tightly encircling a gasket 45in the perimeter of the tubular portion dedicated to wave conduction;the external waveguide 39 further comprises an internal flange 46supporting the interior waveguide 38 and a flange 47 for centering thesame interior waveguide 38 is located under the previous one. Asupporting ring 48 of the interior waveguide 38 is fitted onto theinternal flange 46. A unique transducer 49 is fitted. It has a doublefunction, i.e., it comprises a unique core 50 under which emitting andreceiving piezoelectric components, 51 and 52, are deposited. Dampers 53and 54 are housed behind the piezoelectric components 51 and 52 in thecavities of the core 50. Electrical conductors 55 and 56 connect thepiezoelectric components to portions for signal generation andmeasurement, not shown. Finally, a front blade 57 covers components 51and 52 and provides the connection with waveguides 38 and 39.

The latter embodiments are all designed for interpreting signals in areflection mode, which differs from that of the transmission mode of theembodiment of FIG. 1. Here, no signal returns to the receiver in theabsence of the target. In the presence of the target, the receivingsignal is always present, but has a variable phase lag relatively to theemitted signal depending on the wetting level. When wetting is complete,this phase lag is zero, whereas the phase lag is maximum in the absenceof wetting. A detailed time analysis of the signals should therefore beundertaken here.

Generally, it is important that the waveguides withstand the heat fromthe liquid if the latter is a molten metal. They may be in metal, forexample, or may consist of a casing containing another liquid. It isalso important that the liquid bathing the target, wets them perfectlywhich may sometimes be ensured by coating them with an appropriate body,which does not have any other function but ensuring this wetting.

1. A device for determining the wetting of a wall of an object (2) by aliquid, comprising an enclosure (4) for enclosing a defined volume ofsaid liquid; with said object (2) being immersed in the liquid withinthe enclosure; an emitter and a receiver (15, 16) of ultrasonic waves,and two waveguides (5, 6) extending within the enclosure with theemitter and receiver being respectively mounted on ends of thewaveguides external of the enclosure and with the object (2) beingplaced between the waveguides and having a thickness selected forfavoring the passing of waves from the emitter through the object.
 2. Adevice for determining the wetting of a wall of a object by a liquid,comprising: an enclosure (4) for enclosing a defined volume of saidliquid; with said object (2) being immersed in the liquid within theenclosure; an emitter and a receiver of ultrasonic waves; and twowaveguides passing through the capacity, located side-by-side within theenclosure with the emitter and the receiver being respectively mountedon ends of the waveguides external of the enclosure and with the object(2) being placed in front of the wave guides, the object having a frontsurface with a geometry selected for favoring reflections of the wavesbetween the waveguides.
 3. The device according to claim 1, furthercomprising heating means for heating the liquid within the enclosure andcooling means located external of the enclosure for cooling thewaveguides.
 4. The device according to claim 2, further comprisingheating means for heating the liquid within the enclosure and coolingmeans located external of the enclosure for cooling the waveguides. 5.The device according to claim 3, characterized in that the cooling meansconsists of a case surrounding each of the waveguides between theenclosure and either the emitter or the receiver.
 6. The deviceaccording to claim 4, characterized in that the cooling means consistsof a case surrounding each of the waveguides between the enclosure andeither the emitter or the receiver.
 7. The device according to claim 1,characterized in that the waveguide is covered with a coating whichfavors wetting of the liquid in the enclosure.
 8. The device accordingto claim 2, characterized in that the waveguide is covered with acoating which favors wetting of the liquid in the enclosure.
 9. Thedevice according to claim 3, characterized in that the waveguide iscovered with a coating which favors wetting of the liquid in theenclosure.
 10. The device according to claim 4, characterized in thatthe waveguide is covered with a coating which favors wetting of theliquid in the enclosure.
 11. The device according to claim 1, whereinthe device further comprises a sealing for the enclosure and a heatinsulation system around the waveguides.
 12. The device according toclaim 2, wherein the device further comprises a sealing for theenclosure and a heat insulation system around the waveguides.
 13. Thedevice according to claim 3, wherein the device further comprises asealing for the enclosure and a heat insulation system around thewaveguides.
 14. The device according to claim 5, wherein the devicefurther comprises a sealing for the enclosure and a heat insulationsystem around the waveguides.
 15. The device according to claim 5,characterized in that the sealing system comprises a flange positionedaround a section of the waveguides and joined to a bracket or a sleeveconnected to the enclosure; and the heat insulation system comprises asleeve or insulating bellows extending between the flange and thecooling case.
 16. The device according to claim 7, characterized in thatthe sealing system comprises a flange positioned around a section of thewaveguides and joined to a bracket or a sleeve connected to theenclosure; and the heat insulation system comprises a sleeve orinsulating bellows extending between the flange and the cooling case.17. The device according to claim 11, characterized in that the sealingsystem comprises a flange positioned around a section of the waveguidesand joined to a bracket or a sleeve connected to the enclosure; and theheat insulation system comprises a sleeve or insulating bellowsextending between the flange and the cooling case.